This invention relates generally to integrated circuit (IC) packaging molding processes, and in particular, the present invention relates to substrates for use in IC packaging molding processes.
The packaging molding process involves using a mold press for overmolding an integrated circuit (IC) mounted to a substrate. The overmolding provides an environmental seal. The molding compound itself is a polymeric epoxy material, i.e., a composite consisting of an epoxy resin, an epoxy hardener and a ceramic particle filler, such as silica. IC manufacturers typically receive the molding compound in the form of partially reacted pelletized powder preformed disks. The polymeric material is then processed in a transfer molding press that drives the compound through a heated mold. The heat of the mold causes the viscosity of the molding compound to decrease, allowing it to flow, such that it encapsulates the IC and fills the mold cavity. Once the epoxy resin and hardener completely react, the viscosity of the compound increases until it is hard enough to be ejected from the mold.
In order to set up a mold press for use, several preliminary runs are typically performed with the molding compound to properly establish the temperature, pressure and flow rate on a particular machine. These runs are made without the IC die in place. However, expensive metal-based substrates, such as substrates comprised of bismaleimide triazine (BT) and several metal layers, are routinely used to catch the molding compound after each run through the machine. The cured compound and BT substrates from these preliminary runs are then discarded. Use of expensive substrates in this manner is extremely wasteful and increases production costs substantially.
Additionally, a cleaning cycle is usually run every few hours to keep the mold press in good working order. During this cycle, a pelletized cleaning agent, such as melamine, is run through the mold in the same manner as described above for the molding compound. Again, cleaning runs are made without the IC die in place. However, the expensive metal-based substrates, such as BT substrates, are routinely used to catch the cured cleaning compound. The substrates now containing the cured cleaning compound are then discarded. Conditioning cycles are also run in a similar manner using a conditioning compound for conditioning the mold press. Again, use of metal-based substrates in this manner is very costly.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for a more practical and economical method of collecting used compounds from a mold press.